error: C2027: use of undefined type 'Ui::MainWindow'

RanDev123

I've created a Qt widget application project, the mainwindow just being the default generated mainwindow and after a while the mainwindow.cpp wouldn't compile, even after commenting out everything that I had added to the .h or .cpp, giving the following errors on the initializer and destuctor :
mainwindow.cpp:7: error: allocation of incomplete type 'Ui::MainWindow'
mainwindow.cpp:15: warning: deleting pointer to incomplete type 'Ui::MainWindow' may cause undefined behavior
mainwindow.cpp:7: error: C2027: use of undefined type 'Ui::MainWindow'
mainwindow.cpp:9: error: C2027: use of undefined type 'Ui::MainWindow'
mainwindow.cpp:9: error: C2227: left of '->setupUi' must point to class/struct/union/generic type
mainwindow.cpp:15: warning: C4150: deletion of pointer to incomplete type 'Ui::MainWindow'; no destructor called
Code (Minus previously mentioned commented out bits):
mainwindow.h:
#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
Q_OBJECT

public:
explicit MainWindow(QWidget *parent = nullptr);
~MainWindow();

private:
Ui::MainWindow *ui;

};

#endif // MAINWINDOW_H

mainwindow.cpp:

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
}

MainWindow::~MainWindow()
{
delete ui;
}

This is the same as the default generated class, and another project which complies perfectly and doesn't give any errors, so I'm really confused as to what is happening, any help would be appreciated.

mrjj

Hi and welcome to the forums.
Try to delete the build folder and then Rebuild all.
There can be left overs from other compiles.

RanDev123

@mrjj The error still persists after doing that

SGaist

Hi,

Can you show your .pro file ?

dheerendra

@RanDev123 said in error: C2027: use of undefined type 'Ui::MainWindow':

mainwindow

Looks like you have deleted mainwindow.ui file from the project. Is the file called mainwindow.ui listed under Forms ? Just check you have commented this line in your pro file under FORMS.

RanDev123

@SGaist

#-------------------------------------------------

Project created by QtCreator 2018-12-09T17:41:52

#-------------------------------------------------

QT += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

TARGET = CPU_Simulation
TEMPLATE = app

The following define makes your compiler emit warnings if you use

any feature of Qt which has been marked as deprecated (the exact warnings

depend on your compiler). Please consult the documentation of the

deprecated API in order to know how to port your code away from it.

DEFINES += QT_DEPRECATED_WARNINGS

You can also make your code fail to compile if you use deprecated APIs.

In order to do so, uncomment the following line.

You can also select to disable deprecated APIs only up to a certain version of Qt.

#DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000 # disables all the APIs deprecated before Qt 6.0.0

CONFIG += c++11

SOURCES +=
main.cpp
controlunit.cpp
register.cpp
memorybus.cpp
databus.cpp
addressbus.cpp
controlbus.cpp
arithlogunit.cpp
indatabus.cpp
mainwindow.cpp
alucontrolbus.cpp
memory.cpp
binaryutilities.cpp

HEADERS +=
controlunit.h
register.h
memorybus.h
databus.h
addressbus.h
controlbus.h
arithlogunit.h
indatabus.h
mainwindow.h
alucontrolbus.h
memory.h
binaryutilities.h

FORMS +=
mainwindow.ui

Default rules for deployment.

qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

RanDev123

@dheerendra
Its still there under forms
I can edit its design and stuff, its also still in the project folder and in the .pro file

dheerendra

Do you see following header files under build directory ? > #include "ui_mainwindow.h"

Can you paste the content of the above file ? It is possible that you have changed the object name of MainWindow object in designer.

RanDev123

@dheerendra The class in the ui_mainwindow.h file was called MainWindoe instead of MainWindow, I think I made a spelling mistake when creating the project, but I thought I corrected it in all relevant files, I don't know why this persisted, even after deleting the build folder, I changed the name and it complies now, thank you

dheerendra

Looks like you changed in the names files. Actually you should change the object name in the designer. Look at the property window in Designer. It has property called objectName. Looks like you have changed this also.

enjoysmath

Only way to fix this is to recreate your whole project, dropping in all your source files. At least this gives you an excuse to re-organize your folder structure. This is my second time encountering it and organizing is what I plan to do.

Okay, I was able to fix this by renaming (in QtDesigner to MainWindowClass), compiling, error still there. Rename again to MainWindow. Compile, more errors. Then finally rename it back to MainWindowClass. Save in Qt Deigner. Clean build in VS and rebuild. Errors now gone. VS sucks.